M&S says

Our pure cotton briefs are exceptionally breathable and kind to skin for a fresh feel around the clock. The classic style offers a comfortable fit and is crafted with a keyhole fly for added convenience. These men’s briefs are finished with StayNEW™ technology so they can stay looking bright and fresh wear after wear.

Style

Care and Composition

35 days to return - You may return unused products within 35 days of purchase with a valid parcel summary document. Your items don't need to be in the original box or bag as long as they're securely packaged.How to return
1. FREE returns to select M&S stores
2. Easy returns from home. Simply print the returns label, attach it to the top of your parcel and insert the returns note in the parcel. We will automatically deduct the cost of return from your refund.
To print the returns label and return, simply click here.Tell me more about how to return items and the returns policy